Magnetic field responsive device



April 24, 1945. F. BEACH ET AL MAGNETIC FIELD RESPONSIVE DEVICE Filed Aug. 2, 1941 F1 Ill-.1

2f OUTPUT f INPUT OUTPUT OUTPUT F E- If.

INVENTORS LENNOX F.

BEACH PURVES JOHN C.

THEIR'ATTORNE Patented A r. 24, 1945 MAGNETIC FIELD aasrolssiva DEVICE Lennox r. Beach, Merrick, N. r., and John 0. Purves, Springfield, Mass assignors to The Pllrvea Corporation, Springfield,

poration of Massachusetts Mesa, a cor"- Application Amt 2, 1941, Serial No. 405,162

zclaims.

This invention relates'to the art of magnetic field responsive devices andmore particularly to those devices in which the reluctance or permeability of a magnetic core is periodically varied to render the magnetic condition of the core sensitive and responsive to an external magnetic field. Such devices are known as "fiux valves" and are explained in the Antranikian Patent No. 2,047,609 issued July-14, 1936, inBeach'application Serial No. 348,582 for Direction indicator for magnetic fields, filed July 30, 1940, and in Beach application Serial No. 404,809, for Magnetic field responsive devices, filed July 31, 1941, a ned to the same assignee as the present invention.

. The present invention constitutes an improvement over the prior patent and applications in .that the same cells are used to vary the permeability of the core as are used to pick up the energy corresponding to the external magnetic field. That is, the same coil is used for both'the primary energizing winding and the pick-up winding. This has not been done in the prior art due to the difliculties in attempting to avoid pick-up of the primary or energizing current in the secondary coil, which renders the device insensitive and inaccurate. To avoid such harmful pick-up, the present invention provides a novel balancing arrangement.

Accordingly, it is an object'of this invention to provide a sensitive and simple device responsive to a magnetic field. v

It is a further object of this invention to provide a device of the flux valve" type in which the same windings are used both for primary energizing windings and for secondary pick-up windings.

' conductors 3| connected to a suitable source of periodically varying voltage; This voltage may be alternatingor pulsating in character..' The coils 3, 5, 1, 9 are so positioned that their mag netomotive forces created'by current from source I 1 ,an will be as indicated by dotted arrows 1a. Coils diagonal. The bridge is balanced with ero cxj It is another object of this invention to pro vide, in a device of the flux valve" type, abalanced or bridge arrangement of primary energizing coils which permits the same primary coils to serve as secondary pick-up coils.

Other objects and advantages will be apparent from the specification, taken in connection with the accompanying drawing wherein the inven-. tion is embodied in concrete form.

In the drawing,

Fig. 1 shows both a structural and circuit diagram of one form of the invention.

Figs. 2 to 5 show modifications of the device of Fig. 1.

I In Fig. 1,'two similar coils'3, 5 are placed about a core piece I. Two more similar coils I, 9 are placed about a second core piece II, shown as positioned parallel to core- I' although not necessarily so limited. The ends of core pieces! and H are joined by fiux collector arms l3, 15, being shown, for illustrative purposes only, as fastened by screws ll. Bridging the core pieces l and I'l is a connecting core member II, which is adjust- 3, 5, I, 9 need not be identical, but should create equal magnetomotive forces in core pieces I and II, The value of these magnetomotive forcesis chosenso'as to operate core pieces- I, H on portions of their magnetization curves having varying permeability, whereby these core pieces exhibit varying reluctance to magnetic flux. Adjustable core member 2| is set in .a. position so that, with 'no externalv field, zero output voltage will appear across output conductors 33 connected to conductors 21 and 29.

It will be seen that coils 3,6, l, 9 form abridge arrangement in which the applied voltage from 1 line 3| is applied across one bridge diagonal and the output circuit 3 is connected acrossv the other temal field.

When the device is subjected to an external field, adjacent arms or coils of the bridge are affected differently, in accordance with the principle of operation set forth in the above patent and applications, and opposite coils are affected similarly. The net result is an unbalance of the bridge and the appearance of an alternating output voltage across output conductors 33ihaving a frequency double that 01' the voltage applied to input conductors 3|. This output voltage will reverse phase upon reversal of theextei'nal field, and wllli'depend in magnitude upon the magnitude of the external field, as explained in the above-mentioned prior cases. Hence the output voltage across output conductors 33 may be used in any of the'ways suggested in the above patent and applications, to indicate direction as ln a compass, or to measure magnetic fields.

In connection with the embodiment of our invention hereinabove described and also in connection with the various embodiments thereof illustrated in Figs. 2 through 5, it will be noted that the windings are not only connected to a source of periodically varying current in order to produce periodically varying fluxes in their associatedcores, but'that the same windings are employed to provide a signal voltage output which is induced therein through interaction of the,

device with anexternal magnetic field. Furthermore, it is important tonote that the various circuits are so arranged that exciting voltage com I ponents will not appear in the output circuit but only those voltagecomponents produced by the external field. For example, in Fig. 1, coils 3, 5, 1

and 9 are connected across the input, the coils 3' and 1 and the coils 5 and 9 being connected in series, respectively, thereacross. Therefore, no voltage component from the 'exciting voltage source will appear across the output circuit 33 for the coils of the device is of such magnitude as to operate the permeable cores substantially at the non-linear portion of their magnetization curves whereby to render the device sensitive to an external field.

Fig. 2 shows a modified arrangement of Fig. 1 embodying the same general principles. A core 35 has two identical series connected coils 31, 39 wound oppositely upon it. Connected across these coils is a pair of series-connected identical unilaterally conducting devices 4|, 43 which maybe of any type, such as chemical, electronic, mechanical, etc. Coils 31, 39 need not be identical, but must give equal magnetomotive, forces. A direct current meter 45 is connected between the junction 41 of devices 4|, 43 and, the junction 49 of coils 31, 39. A source of periodic voltage 3| is connected to coils 31, 39. I

Here again there is a bridge-like circuit, which is adjusted to be balanced and yield zero indication on meter 45 when no external field is present. When the device is subjected to an external field, the magnetomotive forces in the portions of the core 35 carrying the two coils 31, 39 are affected difierently bythe external field, and the balance of the circuit is destroyed, permitting current to flow in meter 45. The unilateral conducting device 4|, 43 assure that the meter current is predominantly of one polarity; that is, has a direct current component. The polarity of this component depends on and'corresponds to the direction of the external field.

Fig. 3 shows a modification of Fig. 2. The

same type of coil structure 35, 31, 39 is used.

Meter 45, however, is connected across series connected coils 31, 39. These coils 31, 39 are energized in opposite sense from battery 55 through contacts 5| of a vibrator having energizing coil 52 and armature 53. Vibrator coil 52 periodically interrupts its own energizing circuit, as at contacts 54, in well known fashion. Armature 53 short circuits meter during the intervals that battery 55 is supplying current to coils 31, 39 and in this way, vibrator 52 serves as a source of periodically varying voltage for coils 31, 39 and also as a switching device 'for meter 45, whereby the sense of the meter indication will indicate the direction of the external field. I

Fig. 4 shows a modification of the bridge circult of Fig. 1. Here four separate identical choke coils 51, 59, GI, 63 are used instead of coils 3, 5, 1, 9 of Fig. 1. These coils 51, 59, GI, 63 are placed in the form of a square, and are connected to form a bridge network. If desired, their cores may form a closed square core, or they may be independent, as shown. The directions of their magnetomotive forces created by their energizing currents are indicated by the dotted arrows. Periodically varying input voltage is applied to one bridge diagonal 56, 58 from line 3! and the double frequency output voltage is derived from the other diagonal so, 62 by output conductors 33, as in Fig. l. The theory of operation is similar to that of Fig. 1. V

Fig. 5 shows a further modification of the devices of Figs. 1 and 4, in which two crossed cores 65, 61 each carrying a pair of identical coils H, 15 and 69, 13, are used. The coils are connected exactly as in Figs. 1 and 4, and the operation is similar.

As many changes could be made in the above constructions and many apparently widely diiferent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or'shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claim ed is:

1. In a device ensitive to an external magnetic field and adapted to produce, through interaction with an external field, voltage outputs of double the frequency of the energy employed in exciting said device, an H-shaped core of permeable magnetic material connected together at its ends to form two closed magnetic paths for the circulation of fiux therein having a common leg, a pair of coils mounted on each of the portions of said core extending laterally from said common leg. the coils of each pair being on opposite sides of said common leg, said coils being connected in series in a closed, bridge circuit, a source of periodically varying, exciting voltage connected across one diagonal of the bridge circuit and an output circuit connected across the other diagonal of said bridge circuit, said coils being so constructed, correlated and connected as to buck out components of fundamental, exciting voltage across said output when said bridge is balanced but to supply in non-bucking relation to said output the double frequency voltage components produced in said coils through interaction with the external magnetic field.

2. In a device sensitive to an external magnetic field and adapted to produce, through interaction with an external field, voltage outputs of double 'the frequnecy of the energy employed in exciting said device, a core of permeable magnetic material arranged in the form of a rectangle, a pair of coils on each of the opposite sides thereof, a mag- 1 netic member adjustably connected to said sides .for adjustment longitudinally of said sides, the

coils of each pair being on opposite sides of said member, said coils being connected in series in a closed, bridge circuit, a source of periodically varying, exciting voltage connected across one diagonal of the bridge circuit and an output circuit connected across the other diagonal of said bridge circuit, said coils being so constructed, correlated and connected as to buck out components of fundamental, exciting voltage across said output when said bridge is balanced but to supply in non-bucking relation to said output the double frequency voltage components produced in said coils through interaction with the external magnetic field.

LEN'NOX F. BEACH. JOHN C. PURVES. 

